This invention relates to a helicopter rotor comprising elastomer joints.
In particular this invention relates to a helicopter rotor comprising elastomer joints, which comprises a main shaft provided upperly with a hub in the form of a flat polygonal member extending radially outwards from said main shaft and rigid therewith, said hub comprising a plurality of through apertures closed outwardly by a transverse arm and supporting, at each of said apertures, a blade extending outwards in a substantially radial direction and connected to said hub by means of a yoke extending through the relative said aperture and connected to the relative said arm by means of an elastomer joint; lever means being rigidly connected to each of said yokes and to each of said blades in order to vary the pitch thereof.
In the description given hereinafter, a rotor of the type heretofore defined is indicated by the term "rotor of the type specified".
In known rotors of the type specified, each yoke which connects the blades to the hub of the main shaft is normally constituted by two superposed plates connected at one end to a respective elastomer joint disposed between the yoke and said hub, and connected at the other end to an inner end of the relative blade. Between said two superposed plates a device is normally disposed for controlling the flapping movements of the blade, this device generally comprising a spherical head arranged to selectively engage, according to the angular speed of the main shaft, a plurality of spherical seats provided in a member rigid with the blade.
Although known rotors of the aforesaid type are relatively functional, they have the drawback of possessing a structure which is not particularly compact because of the manner in which their yokes are constructed. Moreover, the concave and convex surfaces which cooperate in controlling the blade flapping movements are relatively delicate and easily deteriorated by external agents.
Finally, the presence of said concave and convex surfaces, the formation of which requires highly complex and precise machining, considerably increases the manufacturing cost of the rotor.